Killer New York real-estate ​​heir Robert Durst walked into a Houston pharmacy to pick up a prescription — and nonchalantly urinated on the cash register and candy rack before walking out,​ cops said.

A warrant for the cross-dressing multimillionaire was issued after he took a leak at a CVS blocks away from his upscale pad at about 12:15 p.m. Sunday, ruining at least $100 in sweets in the bizarre act, which was caught on surveillance video.

“He picked up his prescription, and he then exposes himself and pees all over the cash register and candy at the register and then walks out and walks down the street,” Houston police spokeswoman Jodi Silva told The Post.

“He wasn’t arguing with anybody and he didn’t seem agitated,” Silva said, adding she did not know what the prescription was for. “He just peed on the candy. Skittles, I think.”

The candy rack was removed and a new one was in place Tuesday.

A warrant has been issued charging Durst (inset) with criminal mischief, Silva said. Once he is served, he will be taken to jail to await arraignment, she added.

The wealthy nut’s lawyer, Chip Lewis, said he will address the allegations in court.

​In 2001, Durst, now 71, was arrested as a fugitive and admitted to killing his neighbor and dumping the remains in Galveston Bay. He claimed self-defense and was acquitted of homicide charges.

Durst was also ​the only suspect in the 1982 disappearance of his first wife, Kathleen McCormack, a medical student who vanished after meeting Durst at their South Salem home in Westchester.​

Durst has been cut off from his wealthy family — which runs The Durst Organization, a privately held billion-dollar real-estate company that owns several New York skyscrapers. Last year, he was arrested for trespassing on his brother Douglas’ property at 413 W. 43rd St., and 13 family members have taken out restraining orders against him.

Durst remains free on bail in the trespassing case, and is due back in court Sept. 22. But Manhattan Supreme Court Judge Jill Konviser is likely to move that date up given the Houston charge, and could remand Durst or hike his bail.